(1) Field of the Invention
The present invention relates to status indicator lights for computer systems. More specifically, the present invention implements status indicator lights in thin form factor computer cards.
(2) Art Background
It is quite common for computer systems to have a slot into which may be inserted a thin form factor memory cartridge. A "memory cartridge" is a plug-in module containing random access memory (RAM)) chips that can be used to store data or programs. Memory cartridges are used primarily in portable computers as smaller, lighter, substitutes for disk drives. Memory cartridges typically use a nonvolatile form of RAM which does not lose its contents when power is turned off, or battery-backed RAM, which maintains its contents by drawing current from a rechargeable battery within the cartridge.
To encourage the development of memory cartridges, various standards have been established. One such standard was established by the Personal Computer Memory Card Industry Association (PCMCIA). However, other standards exist, for example, in Japan, JEIDA is the equivalent association to PCMCIA.
The PCMCIA PC Card Standard 2.0 outlines the architecture and specifications for an interchangeable integrated circuit card, with both data storage ("Memory") and peripheral expansion ("I/O") card types defined. Cards interface through a standard 68-pin connector to operate interchangeably in the same 68-pin slot of a host computer system. A variety of devices are now, or will soon be, available, such as RAM, dynamic RAM (DRAM), and flash memory storage products, as well as, modem, facsimile (fax), local area network (LAN), small computer system interface (SCSI) and wireless I/O applications.
The PCMCIA standard primarily defines physical specifications for an interchangeable card. For example, PCMCIA specifies that the width and length of a card must be exactly the same size as that of a credit card. Furthermore, the thickness is specified to be 130 thousandths of an inch (3.3 millimeters) along the edge of the card, and then the center area of the card is allowed to have a maximum thickness of 197 thousandths of an inch (5 millimeters). However, the PCMCIA standard, by itself, does not guarantee interoperability. While it establishes some electrical and software requirements, these requirements are not stringent enough to guarantee that a PCMCIA card will function properly in every manufacturer's PCMCIA slot. Therefore, the exchangeable card architecture (ExCA) standard, which is an extension of the PCMCIA standard, was developed by Intel Corporation. ExCA is a clarifying enhancement of the PCMCIA specification that guarantees interoperability between cards.
Memory cards typically do not have status indicator lights. However, it is desirable for I/O devices to have status indicator lights. An example of a prior art status indicator light for an I/O device is a power light to indicate that the unit has electric power supplied to it. Another example is a link integrity light for a LAN which lights to indicate that the network is functioning properly. Additionally, modems often have transmit and receive indicator lights that light when the modem is respectively transmitting or receiving data.
It is common for the status indicator lights of I/O devices to be light-emitting diodes (LEDs). A LED is a semiconductor device that converts electrical energy into light. LEDs work on the principle of electroluminescence and are highly efficient, producing relatively little heat for the amount of light which is output. Most LEDs are red, although yellow, green and blue LEDs are available. LEDs are also available that emit light in the infrared and ultraviolet ranges.
A right angle surface mount LED is designed to mount to the surface of a printed circuit board (PCB) such that light from the LED is emitted parallel to the surface of the PCB. This is in contrast to more commonly used surface mount LEDs which emit light perpendicularly to the surface of the PCB to which they are mounted. A small form factor right angle surface mount LED is manufactured by the Dialight Company, Manasquan, N.J.
Light pipes are also well known in the art and widely used. A light pipe is an extruded material, such as certain plastic filaments, which provides a path for light. A light pipe is typically used when it is desirable to mount an LED which will act as the light source to a PCB for ease of manufacture, but it is desirable to see the light from the LED at a place remote from the location of the LED. The light pipe is then used to transmit the light from the LED to the remote location. Typical places where light pipes are used include: LED indicators for personal computers, speedometers on automobile dashboards, or consumer electronic components such as video cameras.
The PCMCIA/ExCA specification requires the exterior of an entire card to be opaque. Furthermore, because of the small size of the PCMCIA card, standard LEDs are too large to protrude, or shine diffusely, through the card frame. Therefore, prior art PCMCIA cards have been manufactured without status indicator lights.
Alternately, LEDs have previously been installed into peripheral adapter cables or modules that are connected into PCMCIA I/O Cards. That approach uses additional conductors and pins on the external connector, and increases the bulk of the adapter module itself. A critical requirement for any adapter cable is that it be as small, thin and flexible as possible. Thus, as more LEDs are incorporated into the adapter module, the size increases beyond acceptable limits, and the cable increases in size and becomes less flexible.